Greenhouse gas balance of cropland conversion to bioenergy poplar short-rotation coppice
The production of bioenergy in Europe is one of the strategies conceived to reduce greenhouse gas (GHG) emissions. The suitability of the land use change from a cropland (REF site) to a short-rotation coppice plantation of hybrid poplar (SRC site) was investigated by comparing the GHG budgets of the...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-01-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/95/2016/bg-13-95-2016.pdf |
| Summary: | The production of bioenergy in Europe is one of the strategies conceived to
reduce greenhouse gas (GHG) emissions. The suitability of the land use
change from a cropland (REF site) to a short-rotation coppice plantation of
hybrid poplar (SRC site) was investigated by comparing the GHG budgets of
these two systems over 24 months in Viterbo, Italy. This period corresponded
to a single rotation of the SRC site. The REF site was a crop rotation
between grassland and winter wheat, i.e. the same management of the SRC site
before the conversion to short-rotation coppice. Eddy covariance
measurements were carried out to quantify the net ecosystem exchange of
CO<sub>2</sub> (<i>F</i><sub>CO<sub>2</sub></sub>), whereas chambers were used to measure N<sub>2</sub>O and
CH<sub>4</sub> emissions from soil. The measurements began 2 years after the
conversion of arable land to SRC so that an older poplar plantation was
used to estimate the soil organic carbon (SOC) loss due to SRC
establishment and to estimate SOC recovery over time. Emissions from
tractors and from production and transport of agricultural inputs
(<i>F</i><sub>MAN</sub>) were modelled. A GHG emission offset, due to the substitution of natural gas with SRC biomass, was credited to the GHG budget of the SRC site. Emissions generated by the use of biomass (<i>F</i><sub>EXP</sub>) were also
considered. Suitability was finally assessed by comparing the GHG budgets of
the two sites. CO<sub>2</sub> uptake was 3512 ± 224 g CO<sub>2</sub> m<sup>−2</sup>
at the SRC site in 2 years, and 1838 ± 107 g CO<sub>2</sub> m<sup>−2</sup> at
the REF site. <i>F</i><sub>EXP</sub> was equal to 1858 ± 240 g CO<sub>2</sub> m<sup>−2</sup>
at the REF site, thus basically compensating for <i>F</i><sub>CO<sub>2</sub></sub>, while it was
1118 ± 521 g CO<sub>2</sub> m<sup>−2</sup> at the SRC site. The SRC site could
offset 379.7 ± 175.1 g CO<sub>2</sub>eq m<sup>−2</sup> from fossil fuel
displacement. Soil CH<sub>4</sub> and N<sub>2</sub>O fluxes were negligible. <i>F</i><sub>MAN</sub>
made up 2 and 4 % in the GHG budgets of SRC and REF sites
respectively, while the SOC loss was 455 ± 524 g CO<sub>2</sub> m<sup>−2</sup>
in 2 years. Overall, the REF site was close to neutrality from a GHG
perspective (156 ± 264 g CO<sub>2</sub>eq m<sup>−2</sup>), while the SRC site was
a net sink of 2202 ± 792 g CO<sub>2</sub>eq m<sup>−2</sup>. In conclusion the
experiment led to a positive evaluation from a GHG viewpoint of the
conversion of cropland to bioenergy SRC. |
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| ISSN: | 1726-4170 1726-4189 |